Most people seem to call every type of malware a “virus”, but that isn’t technically accurate. You’ve probably heard of many more terms beyond virus: malware, worm, Trojan, rootkit, keylogger, spyware, and more. But what do all these terms mean? These terms aren’t just used by geeks. They make their way into even mainstream news stories about the latest web security problems and tech scares. Understanding them will help you understand the dangers you’ve heard about. Malware The word “malware” is short for “malicious software.” Many people use the word “virus” to indicate any type of harmful software, but a virus is actually just a specific type of malware. The word “malware” encompasses all harmful software, including all the ones listed below. Virus Let’s start with viruses. A virus is a type of malware that copies itself by infecting other files, just as viruses in the real world infect biological cells and use those biological cells to reproduce copies of themselves. A virus can do many different things — watch in the background and steal your passwords, display advertisements, or just crash your computer — but the key thing that makes it a virus is how it spreads. When you run a virus, it will infect programs on your computer. When you run the program on another computer, the virus will infect programs on that computer, and so on. For example, a virus might infect program files on a USB stick. When the programs on that USB stick are run on another computer, the virus runs on the other computer and infects more program files. The virus will continue to spread in this way. Worm A worm is similar to a virus, but it spreads a different way. Rather than infecting files and relying on human activity to move those files around and run them on different systems, a worm spreads over computer networks on its own accord. For example, the Blaster and Sasser worms spread very quickly in the days of Windows XP because Windows XP did not come properly secured and exposed system services to the Internet. The worm accessed these system services over the Internet, exploited a vulnerability, and infected the computer. The worm then used the new infected computer to continue replicating itself. Such worms are less common now that Windows is properly firewalled by default, but worms can also spread in other ways — for example, by mass-emailing themselves to every email address in an affected user’s address book. Like a virus, a worm can do any number of other harmful things once it infects a computer. The key thing that makes it a worm is simply how it copies and spreads itself. Trojan (or Trojan Horse) A Trojan horse, or Trojan, is a type of malware that disguises itself as a legitimate file. When you download and run the program, the Trojan horse will run...

About Computer Viruses A virus is a program designed by a computer programmer (malicious hacker) to do a certain unwanted function. The virus program can be simply annoying like displaying a happy face on the user’s screen at a certain time and date. It can also be very destructive and damage your computer’s programs and files causing the computer to stop working. The reason why hackers create viruses are open for speculation. The most quoted reason is simply to see if it can be done. Other reasons are Ludite based “smash the machine” motivations, antiestablishment/anti-corporate actions, criminal intent, and various others that range into the “conspiracy theory” realm. Viruses take two basic forms One is a boot sector viruses which infect the section of a disk that is first read by the computer. This type of virus infects the boot or master section of any disks that it comes in contact with. The second is a program virus that infects other programs when the infected program is run or executed. Some viruses infect both and others change themselves (polymorphic) depending on the programs they encounter. Though viruses do not damage computer hardware there have been attempts to create programs that will do things like run the hard drive until it fails or lodge itself in the computer’s clock (which has a rechargeable battery) allowing it to remain active even months after the computer has been unplugged. Other viruses affect certain microchips (BIOS chip for instance). These microchips need to be modified under normal computer use but the virus program can produce changes which cause them to fail. Other viruses will affect the characters or images displayed on the screen which may give the impression of monitor failure. Viruses can cause a great deal of damage to the computers it infects and can cost a lot of time and money to correct it. Computer viruses have been around for a long time, even before computers became widely used and they will likely remain with us forever. For that reason computer users will always need ways to protect themselves from virus programs. The main, common feature of a virus is that it is contagious! Their sole purpose is to spread and infect other computers. A computer gets a virus from an infected file. The virus might attach themselves to a game, a program (both shareware and commercial) or a file downloaded from a bulletin board or the Internet. You cannot get a virus from a plain email message or from a simple text file! That is because the virus needs to be ‘run‘ or executed before it can take effect. This usually happens when the user tries to open an infected program, accesses an infected disk or opens a file with an infected macro or script attached to it. A plain email message is made up of text which does not execute or run when opened. Modern email programs provide the ability to allow users to format email messages with HTML and attach scripts to...